In each treatment period, subjects were admitted to the unit on the day before dosing (Day -1), received a single oral dose of V81444 on Day 1 and, subject to satisfactory medical review, were discharged a minimum of 12 h after dosing. Overall, 3 doses of V81444 were assessed (250 mg, 50 mg, and 100 mg), with 2 subjects included at each dose level. PD assessments were performed at baseline and after each dose of V81444 using PET (with the A2A radioligand, to measure brain A2A RO, as well as MRI techniques to investigate the effects of V81444 on regional brain activity and perfusion during cognitive function tests. PK parameters were assessed by assay of V81444 concentration in plasma. Safety and tolerability were assessed by monitoring physical examination findings, adverse events (AEs), vital signs, 12 lead electrocardiogram (ECG) and clinical laboratory safety tests.